U.S. patent number 5,868,978 [Application Number 08/950,949] was granted by the patent office on 1999-02-09 for injection molding method for thin components.
This patent grant is currently assigned to Matsushita Electric Industrial Co., Ltd.. Invention is credited to Takaaki Higashida, Shinji Kadoriku, Yoshio Maruyama, Keizo Matsumura, Hiroshi Yutani.
United States Patent |
5,868,978 |
Kadoriku , et al. |
February 9, 1999 |
Injection molding method for thin components
Abstract
The separation of a lower mold from an upper mold in an
injection molding machine is either temporarily paused or carried
out at a lower speed so as to maintain deformation of a thin
component within a permissible range, while a jet of air is applied
to help remove the thin component from the upper mold. Also, the
ejecting operation of the thin component is either temporarily
paused or carried out at a lower speed before the deformation of
the thin component exceeds the permissible limit while a jet of air
is applied to help remove the thin component from the lower
mold.
Inventors: |
Kadoriku; Shinji (Takarazuka,
JP), Maruyama; Yoshio (Kyoto, JP),
Higashida; Takaaki (Kadoma, JP), Yutani; Hiroshi
(Katano, JP), Matsumura; Keizo (Hirakata,
JP) |
Assignee: |
Matsushita Electric Industrial Co.,
Ltd. (Osaka, JP)
|
Family
ID: |
18010220 |
Appl.
No.: |
08/950,949 |
Filed: |
October 15, 1997 |
Foreign Application Priority Data
|
|
|
|
|
Nov 21, 1996 [JP] |
|
|
8-310856 |
|
Current U.S.
Class: |
264/40.5;
264/328.1; 425/810; 425/437; 264/335; 425/150; 425/556 |
Current CPC
Class: |
B29C
45/263 (20130101); B29C 45/40 (20130101); B29C
45/1703 (20130101); Y10S 425/81 (20130101) |
Current International
Class: |
B29C
45/17 (20060101); B29C 45/26 (20060101); B29C
45/40 (20060101); B29C 045/43 () |
Field of
Search: |
;264/40.5,328.1,335
;425/150,556,437,810,DIG.102 ;249/66.1 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Heitbrink; Jill L.
Attorney, Agent or Firm: Jordan and Hamburg
Claims
What is claimed is:
1. A method of forming a disk-shaped component with an injection
molding machine, comprising the steps of:
injecting a resin material into a cavity defined by an upper mold
disposed at a stationary plate and a lower mold disposed at a
movable plate to mold the disk-shaped component;
blowing a jet of air into an interface between a formed surface of
the disk-shaped component and the upper mold while simultaneously
opening the upper and lower molds;
pausing the opening of the upper and lower molds temporarily at a
position prior to which an amount of deformation of the disk-shaped
component exceeds a permissible level and allowing the jet of air
to continue separation of the disk-shaped component from the upper
mold; and
restarting the opening of the upper and lower molds after the
formed surface of the disk-shaped component is completely removed
from the upper mold.
2. A method of forming a disk-shaped component with an injection
molding machine, comprising the steps of:
injecting a resin material into a cavity defined by an upper mold
disposed at a stationary plate and a lower mold disposed at a
movable plate to mold the disk-shaped component;
blowing a jet of air into an interface between a formed surface of
the disk-shaped component and the upper mold;
starting opening of the upper mold and the lower mold apart from
one another at a first speed and continuing opening of the upper
and lower mold until the upper mold and the lower mold are spaced
apart a predetermined distance which is less than a distance at
which deformation of the disk-shaped component exceeds a
permissible limit;
reducing a speed of opening the upper mold and the lower mold to a
second speed, which is less than the first speed, when the upper
mold and the lower mold are spaced apart the predetermined
distance;
descending the lower mold at the second speed until the disk-shaped
component is completely separated from the upper mold;
returning the speed of descending the lower mold to the first speed
of opening when the disk-shaped component is completely separated
from the upper mold.
3. A method of forming a disk-shaped component with an injection
molding machine, comprising the steps of:
injecting a resin material into a cavity defined by an upper mold
disposed at a stationary plate and a lower mold disposed at a
movable plate to mold the disk-shaped component;
opening the upper and the lower molds apart from each other to
release the disk-shaped component from the upper mold;
blowing a jet of air into an interface between a formed surface of
the disk-shaped component and the lower mold while further opening
the upper mold apart from the lower mold for releasing the
disk-shaped component from the lower mold by engagement of a
central part of the disk-shaped component with an ejecting
member;
pausing the opening of the upper and lower molds temporarily at a
position before an amount of deformation of the disk-shaped
component due to the engagement at the central part thereof exceeds
a permissible level and allowing the blowing of the jet of air to
completely separate the formed surface of the disk-shaped component
from the lower mold; and
restarting opening of the upper and lower molds after the formed
surface of the disk-shaped component is completely separated from
the lower mold by the blowing of the jet of air; and
ejecting the disk-shaped component to a position for removal.
4. A method of forming a disk-shaped component with an injection
molding machine, comprising the steps of:
injecting a resin material into a cavity defined by an upper mold
disposed at a stationary plate and a lower mold disposed at a
movable plate to mold the disk-shaped component;
opening the upper and the lower molds apart from each other to
release the disk-shaped component from the upper mold;
blowing a jet of air into an interface between a formed surface of
the disk-shaped component and the lower molds;
starting further opening of the upper mold and the lower mold apart
from each other at a first speed for releasing a lower surface of
the disk-shaped component from the lower mold by engagement of a
central part of the disk-shaped component with an ejecting member
until the upper mold and the lower mold are spaced apart a
predetermined distance which is less than a distance at which
deformation of the disk-shaped component at the central part
exceeds a permissible limit;
reducing the speed of opening the upper mold apart from the lower
mold to a second speed, which is less than the first speed, when
the lower mold and the upper mold are spaced apart the
predetermined distance such that deformation of the disk-shaped
component does not exceed the permissible limit;
descending the lower mold at the second speed until the lower
surface of the disk-shaped component is completely released from
the lower mold;
returning the speed of opening the upper mold apart from the lower
mold to the first speed when the disk-shaped component is
completely released from the lower mold.
5. A method of forming a disk-shaped component with an injection
molding machine, comprising the steps of:
injecting a resin material into a cavity defined by an first mold
and a second mold to mold the disk-shaped component;
blowing a jet of air into an interface between a formed surface of
the disk-shaped component and the first mold and simultaneously
separating the first and second molds;
pausing the separating of the first and second molds at a position
prior to which an amount of deformation of the disk-shaped
component exceeds a permissible level and prior to complete
separation of the formed surface of the disk-shaped component from
the first mold;
allowing the jet of air to continue separation of the formed
surface of the disk-shaped component from the first mold; and
restarting the opening of the first and second molds after the
formed surface of the disk-shaped component is completely removed
from the first mold.
6. A method of forming a disk-shaped component with an injection
molding machine, comprising the steps of:
injecting a resin material into a cavity defined by an first mold
and a second mold to mold the disk-shaped component;
opening the first and the second molds apart from each other to
release the disk-shaped component from the first mold;
blowing a jet of air into an interface between a formed surface of
the disk-shaped component and the second mold while further moving
the second mold relative to an ejecting member for releasing the
disk-shaped component from the second mold by engagement of a
central part of the disk-shaped component with the ejecting
member;
pausing the movement of the second mold temporarily at a position
before an amount of deformation of the disk-shaped component due to
the engagement at the central part thereof exceeds a permissible
level and allowing the blowing of the jet of air to completely
separate the formed surface of the disk-shaped component from the
second mold; and
restarting moving of the second mold, after the formed surface of
the disk-shaped component is completely separated from the second
mold by the blowing of the jet of air, to move the disk-shaped
component to a position for removal.
7. A method of forming a disk-shaped component with an injection
molding machine, comprising the steps of:
injecting a resin material into a cavity defined by an first mold
and a second mold to mold the disk-shaped component;
blowing a jet of air into an interface between a formed surface of
the disk-shaped component and the first mold;
starting opening of the first mold and the second mold apart from
each other at a first speed and continuing opening of the first and
second molds until the first mold and the second mold are spaced
apart a predetermined distance which is less than a distance at
which deformation of the disk-shaped component by the opening at
the first speed exceeds a permissible limit;
reducing a speed of opening the first mold and the second mold to a
second speed, which is less than the first speed, when the first
mold and the second mold are spaced apart the predetermined
distance such that deformation of the disk-shaped component does
not exceed the permissible limit;
opening the second mold apart from the first mold at the second
speed until the disk-shaped component is completely separated from
the first mold; and
returning the speed of opening the second mold apart from the first
mold to the first speed when the disk-shaped component is
completely separated from the first mold to position the
disk-shaped component for removal.
8. A method of forming a disk-shaped component with an injection
molding machine, comprising the steps of:
injecting a resin material into a cavity defined by an first mold
and a second mold to mold the disk-shaped component;
opening the first and the second molds apart from each other to
release the disk-shaped component from the first mold;
blowing a jet of air into an interface between a formed surface of
the disk-shaped component and the second mold;
moving the second mold relative to an ejecting member at a first
rate of speed for releasing the formed surface of the disk-shaped
component from the second mold by engagement of a central part of
the disk-shaped component with the ejecting member until the
ejecting member and the second mold are spaced apart a
predetermined distance which is less than a distance at which
deformation of the disk-shaped component at the central part by the
moving at the first speed exceeds a permissible limit;
reducing the speed of moving the second mold to a second speed,
which is less than the first speed, when the second mold and the
ejecting member are spaced apart the predetermined distance such
that deformation of the disk-shaped component does not exceed the
permissible limit;
moving the second mold at the second speed until the second formed
surface of the disk-shaped component is completely released from
the second mold; and
returning the speed of moving the second mold to the first speed
when the disk-shaped component is completely released from the
second mold to position the disk-shaped component for removal.
Description
BACKGROUND OF THE INVENTION
The present invention relates to a method and an apparatus for
injection molding of various thin components, such as optical disk
substrates and magnetic recording mediums, which are made of
synthetic resin and have relatively wide flat surfaces.
In a conventional injection molding machine as shown in FIGS. 7A
and 7B, optical disk substrates are formed in a cavity 53 between
two molds 51 and 52 at a stationary plate side and at a movable
plate side, respectively. In a curing process of a resin material
during the molding operation, a sprue portion 54a is separated from
the optical disk substrate 54 by lifting up a gate cut punch 62
mounted at the center of the movable plate from a position shown in
FIG. 7A to a position shown in FIG. 7B. The two molds are then
opened after the optical disk substrate 54 is cooled down and cured
by releasing heat to the molds. Generally, in order to minimize the
duration required for the molding cycle, a jet of air is applied
from slots 55 in the mold to the interface between the optical disk
substrate 54 and the mold 51 while the molds are being opened at a
high speed so as to swiftly cool down and separate the optical disk
substrate 54 from the mold 51 at the stationary plate side.
After the separation of the two molds, the optical disk substrate
54 and the sprue portion 54a are ejected out by an eject rod (not
shown), which is mounted at the center of the movable plate,
lifting up in a sequence a sprue eject rod 56 and a substrate eject
rod 57, both being joined to the mold 52, as shown in FIGS. 8A-8C,
while a stream of air is applied from slots 58 in the mold 52 to
the other side of the optical disk substrate 54 to ease the removal
of the optical disk substrate 54 from the mold 52.
After the completion of the ejecting operation, the optical disk
substrate 54 and the sprue portion 54a are transferred from the
injection molding machine to the outside by a pickup device (not
shown).
There is a demand for further reduction of the molding cycle. In
order to achieve this object, it is essential to minimize the time
for cooling. The cooling time at the time of separating the molds
is, however, substantially short, and further reduction of the time
may lead to undercooling of the substrates. If the temperature
during the separation of the molds and the ejection of the optical
disk substrate 54 becomes higher than a thermoforming temperature
of the resin material, the resistance generated when the optical
disk substrate 54 is separated from the molds 51 and 52 or the
moment generated between the center and the rim of the optical disk
substrate 54 when its central part is lifted up while the rim is
not fully separated from the mold may cause a deflection or bend in
the optical disk substrate 54 as shown in FIG. 8C.
BRIEF SUMMARY OF THE INVENTION
It is an object of the present invention to minimize the duration
of time for the cycle of molding thin components by accelerating
the cooling and the separating operations at the time of opening
the molds with an intensive jet of air, without exceeding a
permissive level of deformation in the thin components.
To accomplish the object, the present invention is characterized in
that, in an injection molding process of thin components, such as
optical disk substrates, when upper and lower molds are opened
after a thin component is formed in a cavity between the molds, a
jet of air is applied from the upper mold side to an interface
between an upper surface of the component and the upper mold at a
stationary plate, while the mold separating operation is
temporarily paused at a position where the amount of deformation of
the component reaches a permissive limit, and restarted after the
entire surface of the component is removed from the upper plate by
the air jet.
According to such arrangement, the deformation of the thin
components over the permissive limit is restricted by the amount of
separation of two molds, while the thin component can be more
quickly removed from the lower mold at the stationary plate side by
an intensive jet of air for a shorter time. Also, as the component
can be cooled down faster with the help of the air jet, the
deformation of the component is further prevented. Apart from the
period during which the mold separating action is paused, the
operation is carried out at a high speed, thus reducing the time
for the molding cycle without presenting problems of deflection or
bend of the thin components.
Other and further objects, features and advantages of the invention
will appear more fully from the following description.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a schematic view of an injection molding machine for
forming an optical disk substrate;
FIGS. 2A-2C are cross-sectional views of the injection molding
machine of FIG. 1, respectively showing a state in which the mold
separation is started, a state in which an optical disk substrate
is being removed from the mold at an early step of the ejecting
operation, and a state in which the optical disk substrate and its
sprue portion are being ejected for removal;
FIGS. 3A-3C are time charts showing the changes in the state of the
injection molding machine of FIG. 1 before the ejecting operation
is started, in which FIG. 3A represents the position of a lower
mold at a movable plate side, FIG. 3B represents the speed of
separating movement of the lower mold, FIG. 3C represents the
action of air blowing across an upper mold at a stationary plate
side, and FIG. 3D represents the state of the optical disk
substrate being removed from the upper mold at the stationary plate
side;
FIGS. 4A-4C are time charts showing the changes in the state of the
injection molding machine of FIG. 1 before the ejecting operation
is started according to a modified embodiment, in which FIG. 4A
represents the position of a lower mold at a movable plate side,
FIG. 4B represents the speed of separating movement of the lower
mold, FIG. 4C represents the action of air blowing across an upper
mold at a stationary plate side, and FIG. 4D represents the state
of the optical disk substrate being removed from the upper mold at
the stationary plate side;
FIGS. 5A-5C are time charts showing the changes in the state of the
injection molding machine of FIG. 1 after the ejecting operation is
started, in which FIG. 5A represents the position of a lower mold
at a movable plate side, FIG. 5B represents the speed of separating
movement of the lower mold, FIG. 5C represents the action of air
blowing across the lower mold at the movable plate side, and FIG.
5D represents the state of the optical disk substrate being removed
from the lower mold at the movable plate side;
FIGS. 6A-6C are time charts showing the changes in the state of the
injection molding machine of FIG. 1 after the ejecting operation is
started according to a modified embodiment, in which FIG. 6A
represents the position of a lower mold at a movable plate side,
FIG. 6B represents the speed of separating movement of the lower
mold, FIG. 6C represents the action of air blowing across the lower
mold at the movable plate side, and FIG. 6D represents the state of
the optical disk substrate being removed from the lower mold at the
movable plate side;
FIGS. 7A and 7B are cross-sectional views of a conventional
injection molding apparatus, respectively showing a state in which
the ejecting operation of a sprue portion has started, and a state
in which the sprue portion has been completely separated; and
FIGS. 8A-8C are cross-sectional views showing the changes in the
state of the conventional injection molding apparatus after the
ejecting operation is started, respectively showing a state in
which the mold separation has been started, a state of an early
stage of the ejecting operation, and a state of the optical disk
substrate being removed by an upward thrust at its central
portion.
DETAILED DESCRIPTION OF THE INVENTION
Preferred embodiments of the present invention will be hereinafter
described referring to FIGS. 1 to 6.
An optical disk substrate B shown in FIGS. 2A-2C is formed using an
injection molding machine A shown in FIG. 1. The injection molding
machine A includes an upper mold 2 downwardly fixed to a stationary
plate 1 at a side where a resin material is injected and a lower
mold 4 supported by a movable plate 3 for opening and closing
actions as shown in FIG. 1. The resin material is injected into a
cavity 5 defined between the two molds 2 and 4 to form a thin
component such as an optical disk substrate. The cavity 5 comprises
a sprue region 5a, through which the resin material is injected,
and a substrate region 5b where the optical disk substrate B is
shaped from the resin material injected through the sprue region
5a.
The movable plate 3 is connected by a link 7 to and driven
vertically by an actuator 6 for opening and closing the lower mold
4. Various movements of the lower mold 4, including the start,
stop, and pause, as well as the operation speed, are controlled
with motion signals transmitted from a controller 9, such as a
microcomputer, to the actuator 6.
The lower mold 4 is provided with a gate cut punch 8 driven
vertically by a hollow cylinder 17 mounted to the movable plate 3.
A sprue eject rod 13 and a substrate eject rod 14 are driven by an
eject rod 12 fixedly mounted to a base (not shown) in a sequence
and at a given ratio of motions in accordance with progression of a
mold separating action as shown in FIG. 2. The hollow cylinder 17
is actuated with a solenoid valve 27 which is connected to a
conduit 17a of the cylinder 17 and timely controlled by motion
signals from the controller 9.
The upper mold 2 is provided with an air feeding means 21 for
applying a jet of air from slots 11 to an upper surface B2 of the
optical disk substrate B formed in the cavity 5. Similarly, the
lower mold 4 is provided with an air feeding means 22 for applying
a jet of air from slots 15 to a lower surface B3 of the optical
disk substrate B formed in the cavity 5. Each of the air feeding
means 21 and 22 has its respective air feeding conduits 21a and 22a
communicated to their corresponding slots 11 and 15 provided in the
molds 2 and 4. The solenoid valves 23 and 24, respectively mounted
to the air feeding conduits 21a and 22a, are controlled by motion
signals from the controller 9 to apply and stop the jets of
air.
The sprue region 5a, in the upper mold 2, is connected across the
stationary plate 1 to an injection cylinder 25. The injection
cylinder 25 has an interior space 25a into which a given amount of
the resin material in liquid form is supplied from a preplastic
heat cylinder 26. The resin material is injected into the cavity 5
by the action of a plunger 25b of the injection cylinder 25. The
start and stop actions of the cylinders 25 and 26 and the amount of
the resin material to be injected are controlled by motion signals
from the controller 9.
For those controlling operations, the controller 9 includes an
operation panel 9a for entering data of the operating modes and
parameters. Programs for controlling the molding operation may be
saved in either an external storage medium or a built-in memory of
the controller 9.
The resin material filled in the cavity 5 is cooled down by heat
radiation to the molds 2 and 4 and gradually cured from the sides
near the molds 2 and 4.
In this cooling process, the gate cut punch 8 is lifted up by
action of the hollow cylinder 17 mounted to the movable plate 3
thus separating a sprue portion B1 from the optical disk substrate
B formed of the resin material shaped in the cavity 5 between the
two molds 2 and 4 as shown in FIGS. 2A-2C. The temperature at a
central part of the resin material forming the optical disk
substrate B is measured with a thermal sensor 31. The cooling
process is continued with the molds remaining closed until the
controller 9 judges that the resin material is cooled down to its
thermoforming temperature. For example, in case that the resin
material is polycarbonate, the molds 2, 4 are kept closed until the
temperature reaches about 145.degree. C. which is close to the
thermoforming temperature of about 126.5.degree. C. of
polycarbonate. If the cooling time required for the resin material
is known, it is also possible to preliminarily input the data
regarding the cooling time in the controller 9, based on which the
molds 2, 4 are kept closed until the resin is cooled down to a
certain temperature. After the cooling, the jet of air is applied
by the air feeding means 21 to the interface between the upper mold
2 and the upper surface B1 of the optical disk substrate B, as
shown in the timing chart of FIG. 3C, while at the same time the
movable plate 3 is descended by the link 7 driven by the actuator 6
as shown in FIG. 3A. The molds 2, 4 are opened up to a position
within a permissive range of deformation of the optical disk
substrate B. A state of the molds 2, 4 slightly separated from each
other by a distance of 0.1-0.3 mm is shown in FIG. 2A by a phantom
line which, for simplifying the illustration, denotes the upper
mold 2 shifted from the lower mold 4. The opening motion is paused
at the point t1 shown in FIG. 3A where the lower mold 4 is away
from the upper mold by the distance of 0.1-0.3 mm. The separation
of the molds 2, 4 is restarted either from the point t2 when the
optical disk substrate B is separated from the upper mold 2 by the
air jet or the point t3 when the cooling with a flow of air 11a
across the upper mold 2 has been sufficiently supplied, as shown in
FIG. 3A. Both separating actions of the molds 2, 4 described above
are carried out at a high speed S0 as shown in FIG. 3B. The jet of
air from the air feeding means 21 is stopped at the point t3'
between t3 and t4 as shown in FIG. 3C during the separation of the
molds when the molds 2 and 4 are so widely separated from each
other that the air jet provides little effect.
A modified example of the embodiment is shown in the timing charts
of FIGS. 4A-4D, in which the descending speed of the lower mold 4
is decreased to a low rate S1 (FIG. 4B) from the point t1 to the
point t3, and the duration tm therebetween is set to be identical
with that of the embodiment described in conjunction with FIGS.
3A-3D.
Although the jet of air is applied across the upper mold 2 on the
stationary plate 1 side to the upper surface of the optical disk
substrate B during the mold separating action similar to with the
prior art arrangement, the separating action in this embodiment is
paused before the lower mold 4 reaches a point where the
deformation on the optical disk substrate B exceeds the permissive
level. In a modified embodiment shown in FIG. 4, the speed of the
lower mold 4 is decreased to a slower speed S1 during the time when
air is blown on the upper surface B1 of the optical disk substrate
B to be removed from the upper mold 2 before the lower mold 4
reaches a point where the amount of deformation on the optical disk
substrate B exceeds the permissive level. The application of the
air jet is more intensive but shorter in duration hence allowing
the optical disk substrate B to be removed from the upper mold 2
quickly and to be cooled down to the thermoforming temperature. The
deformation of the optical disk substrate B is thereby restricted
by controlling the amount of separation of the lower mold 4 from
the upper mold 2. After the resin material is cooled down, the
molds 2, 4 are separated at the high speed S0. Accordingly, the
time for removing the optical disk substrate B from the upper mold
2 at the stationary plate 1 side and cooling down the same in the
cycle of the molding operation is effectively minimized without
presenting problems of deflection or bending of the optical disk
substrate B.
After the lower mold 4 has reached the point t4, shown in FIGS. 3A
and 4A, by further descending the movable plate 3 to start the
ejecting operation, the lower mold 4 is further separated from the
upper mold 2 so as to cause the sprue eject rod 13 to be pushed by
the eject rod 12 fixedly mounted to the base (not shown), for
ejecting out the sprue portion B1 as shown in FIG. 2B. When the
separation of the molds further proceeds to a point t5, shown in
the time chart of FIG. 5A, where the sprue portion B1 is ejected
out by a distance of 4 mm, the substrate eject rod 14 is lifted up
about 0.1 mm to 0.3 mm, as a result of which the central part of
the optical disk substrate B is removed from the lower mold 4 by
0.1 to 0.3 mm as shown in FIG. 2B.
The separating operation of the molds is paused at a point t6 where
the central part of the optical disk substrate B is slightly
removed from the lower mold 4. Meanwhile, the air supplying means
22 starts to blow a jet of air across the slots 15 in the lower
mold 4 to the lower surface B3 of the optical disk substrate B at a
proper point t4' between the point t4 where the ejecting operation
is started and the point t5 where the sprue eject rod 13 is
projected out as shown in FIGS. 5A and 5C. The point t4' is
preferably set just before the point t5, for achieving optimum
effects of the air jet. The separation of the molds is restarted at
a point t7 shown in FIG. 5A where the lower surface B3 of the
optical disk substrate B has been completely removed from the lower
mold 4 by the blown air 15a. Then, the substrate eject rod 14 is
further lifted up about 1.5 mm after the point t7, which causes the
inner periphery of the sprue portion B1 to be lifted up higher than
the gate cut punch 8 as shown in FIG. 2C. The sprue portion B1 is
continued to be thrust up by the sprue eject rod 13 to be further
higher than the optical disk substrate B for easy removal
therefrom, and the mold separating operation is terminated. The
optical disk substrate B and its sprue portion B1 are then
automatically taken out from the injection molding machine.
Meanwhile, the air jet from the air supplying means 22 is stopped
and the movable table 3 is returned to its eject start position to
end the ejecting operation.
Alternatively, as shown in timing charts of FIGS. 6A-6D, the speed
of the mold separating operation may be decreased to a lower speed
S1 either from the point t5 where the substrate eject rod 14 is
started to be thrust up or the point t6 where the mold opening
operation is temporarily paused to the point t7 where the central
part of the optical disk substrate B is slightly (0.1 mm-0.3 mm)
removed from the lower mold 4, while blowing air from the slots in
the lower mold 4 to entirely remove the lower surface B3 of the
optical disk substrate B from the lower mold 4 before reaching the
point t7.
In this embodiment and its modification described above, during the
ejecting process of the optical disk substrate B after the mold
separating operation, a jet of air is blown to the interface
between the lower surface and the optical disk substrate B from the
lower mold 4 simultaneously with the start of the ejecting
operation, similar to the prior art arrangement. In this
embodiment, however, the ejecting action is temporarily paused
before the deformation at the center of the optical disk substrate
B being thrust up exceeds a permissible level. Alternatively, in
the modified embodiment, the speed of ejecting action is reduced to
a lower speed S1 before the deformation at the central part of the
optical disk substrate B exceeds a permissive level, so as to
entirely remove the lower surface B3 of the optical disk substrate
B from the lower mold 4 by the air jet.
By this arrangement, the deformation of the optical disk substrate
B is restricted to within the permissible range by controlling the
amount of thrust on the optical disk substrate B, and the substrate
B is more quickly removed from the lower mold 4 by an intensive jet
of air for a shorter time. The air jet also helps to further cool
down the optical disk substrate B to prevent unwanted deformation
caused by heat. After the removal of the substrate, the ejecting
operation is continued at a high speed S0, thus reducing the time
required for the removal of the substrate B from the lower mold 4
without presenting problems of deflection or bending of the optical
disk substrate B.
Although the present invention has been fully described by way of
examples with reference to the accompanying drawings, it is to be
noted that various changes and modifications will be apparent to
those skilled in the art. Therefore, unless otherwise such changes
and modifications depart from the scope of the present invention,
they should be construed as being included therein.
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